After some time I realized that auto-complete was working well when I don't have yasnippet, so that's not the solution. I've also tried (yas/initialize) and (yas--initialize) but it's not making any difference. I've also launch yasnippets before and after autocomplete, and the result is the same. I've also tried modifying the yas/trigger-key variable, and always I have the same result. Hopefully you can help me.

What versions of auto-complete and yasnippet are you using? At one time, the latest yasnippet and ac-source-yasnippet did not work together, though I'm not sure if that's still the case. I set ac-source-yasnippet to nil in my init.el.
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jpkottaApr 4 '13 at 22:32

It's working with that!!! thanks, still I'm going to search a little bit further, because it's kind of weird to have ac-source-yasnippet set to nil. Isn't there any trouble because of that in your configuration?
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silgonApr 13 '13 at 9:49

It is kind of weird, but I don't think it causes problems for me. Both yasnippet and autocomplete work fine. Looking at the source code, it seems like removing it from ac-sources (which is buffer local) might be more correct.
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jpkottaApr 15 '13 at 22:18

Ok, not problem has been generated until now, thanks a lot!
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silgonApr 18 '13 at 13:03